The Brain and Special Senses Flashcards
What is olfaction?
Smelling
Describe the structure of the nose and special sense organ:
- Nasal cavity
- lined with mucus
- Olfactory epithelial on cavity roof
- Olfactory epithelial has receptor cells in it
- Olfactory nerves pass through cribriform plate to Olfactory bulb
- Olfactory tract
Describe the process of olfaction:
- Air enters the nasal cavity
- Upon reaching the olfactory organs, lipid and water soluble molecules diffuse into the mucus
- Dissolved chemicals interact with cilia on each receptor end
- Binding of odorants changes receptor permeability causing an action potential
- Information is relayed to Olfactory cortex from the olfactory bulb through the olfactory tract
What makes up the olfactory organs?
- Olfactory epithelial
- Olfactory glands
What are papillae?
- projections or bumps on the tongue with many taste buds
name the 3 types of papillae: and number of taste buds on each
- Filiform (0)
- Fungiform (5)
- Circumvallate (100)
What are taste buds and where are they found?
- Bundles of 50-150 taste receptor cells and specialised epithelial
- Found in walls of papillae
How do chemicals reach gustatory receptor cells?
- small microvilli of each receptor cell extend through the taste pore into the fluid with the chemicals
name the 6 Tastes
1) Sweet
2) Salty
3) Sour
4) Bitter
5) Umami
6) Water
how do we taste things?
Dissolved chemicals contact taste hairs depolarising the membrane resulting in an action potential
What is the nerve pathway for tasting?
- Gustatory cells stimulate cranial nerves 7,9 and 10.
- These all synapse within the nucleus in a solitary tract of the Medulla Oblongata
- Taste information is then sent to the Thalamus
- The information is finally sent to the gustatory cortex
Definition of refraction:
The bending of light when it travels from one medium to another
In light what happens to rhodopsin?
Rhodopsin splits into Opsin and Retinal because the structure Retinal changes (bleaching)
Describe the nerve pathway from the eyes to the visual cortex:
- Nerve fibres from each eye travel along the optic tract until reaching the optic chiasm (cross over)
- At the chiasm half the nerve fibres from each eye cross over to reach the thalamus on the opposite side
- Nuclei in the thalamus relay visual information to the reflex centres in the brain stem and then to the visual cortex
What does the middle ear contain?
3 auditory ossicles
- malleus
- incus
- stapes
what is another name for the ear drum?
Tympanic membrane
list all the features needed in the process of hearing:
- Tympanic membrane
- Malleus
- Incus
- Stapes
- Oval Window
- Vestibular duct perilymph
- Cochlear duct endolymph
- Basilar membrane
- Organ of Corti
Describe the process of hearing:
- Soundwaves vibrate tympanic membrane
- Vibrations are relayed through auditory ossicles
- The stapes vibrates the oval window causing pressure waves through the vestibular duct perilymph
- The waves travel through the cochlear duct endolymph
- These waves vibrate the Basilar membrane, which contains the organ of corti
- Organ of Corti contains mechanoreceptors, which have hairs.
- The hairs are bent due to the vibrations causing an AP along the cochlear nerve
What is the pathway of the nerve:
- Information is passed along cochlear branch of vestibulocochlear neve
- This is taken to the medulla oblongata and synapsed at the cochlear nucleus
- Then to the thalamus
- Then to the auditory cortex
What is the vestibular system?
Equilibrium, and balance
What is the Vestibular apparatus?
- Semi circular canals
- Otoliths
Describe the structure of the semi circular canals:
- 3 loopy canals next to the cochlea
- At the base of each loop are Ampulla
- An ampulla contains a Capula, Cristae and stereocilia (
- Loops are filled with endolymph
How is head movement detected?
- When the head moves the endolymph moves, increasing pressure on the Capula, bending the stereocilia causing an AP
What are Otoliths?
Organs that detect forward, backward movements and gravity
